Wireless backhaul networks are deployed to carry the traffic between a wireless access network and the core network. For example, a wireless backhaul network may comprise a plurality of hubs, each connected to the wired core network, via Ethernet. Each hub serves multiple remote backhaul modules (RBMs), in a point to multipoint or point to point configuration, using a wireless channel. Each RBM is deployed close to an access network base station, such as a small cell base station, and connected to the base station via a cable. The hubs are deployed at the locations where wired high capacity access to the core network is available, e.g. at a fiber point-of-presence.
In a wireless backhaul network, the term cluster refers to a number of RBMs and their respective serving hub. Performance of an RBM, such as throughput, is contingent upon its received carrier-to-interference-plus-noise ratio (CINR) and the amount of bandwidth allocated to this RBM given a selected carrier. The received signal strength of an RBM is determined by the transmit power of its serving hub and the pathloss between the serving hub and the RBM.
The received interference-plus-noise level of an RBM is determined by the transmit powers of all the interfering hubs and the pathlosses between interfering hubs and the RBM. An RBM is affected by an interfering hub when a desired signal and an interfering signal are transmitted over the same carrier frequency.
In orthogonal frequency division multiple access (OFDMA) networks, the frequency resources are divided into subcarriers or tones. In frequency reuse of 1 multi-sector deployment, the interference-over-thermal noise (IoT) of each hub can vary greatly from one frame to another, due to different RBMs scheduled in transmission in different frames. Hence, effective uplink power control is necessary to mitigate the interference received at the hubs.
In the literature, many heuristic power control schemes have been proposed. Two commonly used power control schemes in uplink systems are Fractional Power Control (FPC) and Geometric power control (GPC). Reference is made to:
(1) Simonsson, A.; Furuskar, A., “Uplink Power Control in LTE—Overview and Performance: Principles and Benefits of Utilizing rather than Compensating for SINR Variations,” Vehicular Technology Conference, 2008. VTC 2008—Fall. IEEE 68th, vol., No., pp. 1-5, 21-24 Sep. 2008, which describes a method using Fractional Power Control (FPC); and(2) Senarath, Gamini, et al., U.S. patent application Ser. No. 12/633,657, Senarath, Gamini, et al., entitled “System and Method for Power Control.” which describes a method using Geometric Power Control (GPC).
As applied to a wireless backhaul network, for FPC, the transmit power of each RBM is given byPTXFPC=max { min {Pmax,P0+αPLserv},Pmin}where P0 is the target per-tone received signal strength, α is a pathloss compensation factor, PLserv is the pathloss between the RBM and its serving hub, Pmin is the minimum per-tone transmit power, Pmax is the maximum per-tone transmit power, and PTXFPC is the per-tone transmit power governed by the FPC algorithm.
For GPC, the transmit power of each RBM is given byPTXGPC=max { min {Pmax,PTXFPC+βCINRDL},Pmin}where CINRDL is the received CINR of the RBM in downlink from its serving hub (i.e., downlink geometry), β is a tunable parameter, and PTXGPC is the per-tone transmit power governed by the GPC algorithm.
Most of the existing power control schemes, including FPC and GPC, however, require a computationally expensive parameter search. For instance, there are 2 parameters in FPC and 3 parameters in GPC to optimize. More importantly, if there is any change in the radio frequency (RF) and/or interference environments, those parameters need to be optimized again, which might not be feasible, in practice.
An object of the present invention is to provide an improved or alternative method and system for uplink power control in wireless networks, particularly for wireless backhaul solutions comprising fixed or stationary nodes with directional antennas, including small cell non-line-of-sight (NLOS) wireless backhaul networks.